Electronic Ballasts: Relief for the Senses
Electronic Ballasts: Relief for the Senses
New research on fluorescent lighting indicates that light modulaton ("flicker") at invisible frequencies from conventional fluorescent lighting may induce discomfort in humans claiming hypersensitivity to electricity. If this turns out to be true, it would make the flicker-free electronic ballasts even more attractive.
Although hypersensitivity to electricity seems to be a reality for many people, no coherent theory has yet been proposed that can explain the condition. Some researchers suggest that electric and magnetic fields of certain frequencies interfere with the nervous system; however, others believe that hypersensitivity is a psychosomatic illness, and the syndrome has even been considered a type of hypochondria. Often, but not always, the problems first appear in front of a computer's video screen or with fluorescent lamps. Thereafter, many patients experience hypersensitivity to AC cables and several other electrical devices.
Whatever the cause, the condition is a very serious handicap for the people who experience it. Many of the sufferers cannot work in an office, and some of them feel compelled to move out to remote areas where they live in houses without electricity.
But electric and magnetic fields may not be the only sources of the syndrome. Preliminary findings made by investigators at the Institute for Working Life (Arbetslivsinstitutet) in Solna, outside the Swedish capital Stockholm, indicate that light modulation ("flicker") at invisible frequencies plays a central role. Most lamps fed by alternating current produce light which varies with the AC cycle. This is not exactly the same thing as flicker because it cannot actually be seen; the difference between the strongest and weakest light is too small, and the cycles are too short. But the light modulation at this frequency can still influence the nervous system.
THREE PARAMETERS
In this study, a group of 14 people claiming to be hypersensitive to electricity and a control group of 14 people were exposed alternately to fluorescent light from systems with conventional or high-frequency (HF) electronic ballasts. The lamps were hidden behind an opaque screen, and there was no way of telling which lamps were switched on at a given moment. Three parameters-two subjective and one objective- were registered during each of four consecutive 15-min periods. The persons gave a subjective rating of their symptoms and a rating of how they experienced the light quality. EEG alpha activity in the brain was also measured.
The result was highly significant: 9 of the 14 subjects in the hypersensitive group felt better with HF light than with conventional light, and 10 judged the HF light to be of better quality. In nine of the hypersensitive persons, EEG alpha activity was higher when exposed to light from conventional lamps/ballasts. Moreover, for 7 of the 14 subjects within the hypersensitive group, there was a match between all three parameters.
No one in either group claimed that they could actually discern the difference between light types.
These results should be considered significant since the group of hypersensitive people could be described as "self-defined": this group specifically described their symptoms as related to fluorescent lighting, and could thus be expected to be heterogeneous. Moreover, if these people suffer from a psychosomatic illness one would have expected them to respond negatively to all forms of fluorescent light. This was not the case, however.
LESS PROBLEMS IN FACTORIES
Most lamps running on alternating current have a modulation since they turn on and off at twice the frequency of the AC. But the modulation is higher for some lamps and lower for others. Although incandescent lamps also show rapid fluctuations in light intensity, the filament does not cool off enough to dim very much in 0.01 seconds. Thus the modulation for incandescents is only 5-10%. (See figure)
Fluorescent lamps have less thermal inertia, and thus more modulation. Older, 38-mm-diameter (T12) lamps have a 20% modulation, whereas the more modern 26-mm (T8) lamps have a 35-40 % modulation-with conventional ballasts.
Electronic HF ballasts, on the other hand, transform the standard 50 or 60 Hz AC to 20-60 000 Hz. One of the incidental advantages of HF lighting is extremely low modulation (ca 1%).
Roger Wibom, who designed and performed the experiment together with Per Nylén, says that one of the clues that led to the modulation hypothesis was that hypersensitivity is often observed in offices but almost never in factories. And this makes sense: the triphasic current used in factories dampens the modulation considerably-from 20 to just a few per cent in the case of the older T12 lamps.
The experiment would have been hard to perform in a normal environment since any magnetic fields created during or before the 15-min runs could have influenced the results or the experimental subjects' willingness to take part. For that reason, a mobile laboratory (a bus) was fitted with the experimental equipment. All cables, transformers, etc, were screened to ensure the patients that the laboratory was free from electromagnetic fields. Although some of the hypersensitive persons lived in far-off places, they were able to take part in the experiment since the bus could be driven out to their homes.
SENSIBLE PEOPLE
"Some of the people who took part in the experiment have bought high frequency fluorescent lamps and say they feel better", says Per Nylén. As he is not apt to jump to conclusions, he quickly adds: "But then there might be a placebo effect."
Some scientists have completely dismissed the hypersensitivity syndrome as hypochondria, or they consider it to be psychosomatically induced, an attitude that Nylén finds very unfair. "The majority of those people struck me as being very sensible."
Wibom and his colleagues are very eager to repeat the experiments with more participants and are also preparing for similar experiments with CRT computer video screens with variable frequencies.
There is still no solid theory that could explain the mechanism by which modulating light could have such effects. Nylén does not exclude the possibility that hypersensitive persons represent a distinct group. But, they might also be at the extreme end of a perhaps genetically defined continuum of sensitivity. Maybe some people who do not claim hypersensitivity would still feel more at ease with low-modulation lighting.
The researchers do not rule out electromagnetic fields as a major or complementary cause of the hypersensitivity phenomenon. But several research efforts aimed at establishing a cause-effect relationship between electromagnetic fields and hypersensitivity have not yielded conclusive results, says Nylén's colleague Roger Wibom.
It would be difficult-if not impossible-and expensive to shield workers from electromagnetic fields in a workplace. However, if the problem for some of the hypersensitive people is not the electromagnetic fields but mainly light modulation, there would be a quick and easy fix-which is also highly compatible with the goal of increasing energy efficiency.
Fredrik Lundberg
The report Flimmer från lysrör: En möjlig orsak till besvär vid "elöverkänslighet" ("Flicker from fluorescent lighting: A possible cause for hypersensitivity to electricity". - In Swedish) can be ordered from:
Arbetslivsinstitutet, S-171 84 Solna, Sweden
Fax:+46 8 730 98 88